1. Field of the Invention
The present invention relates to new and useful chemical compounds, specifically to a unique type prepared with methylol phenol and maleic monomers which interact through independent condensation pathways and form crosslinked polymers.
2. Description of the Related Art
There is a countless list of polymers which contain phenolic groups, dating back to the invention of bakelite in the early part of this century. There also are many known polyesters, either saturated or unsaturated. Phenolic polymers belong to the thermoset type, which means they are crosslinked. Polyesters can also be crosslinked, particularly those of the unsaturated type. However, there are no known crosslinked phenolic polyesters because the chemistry that brings together these two big families has not been fully expanded. Phenolic prepolymers are rich in methylol groups or methylene bridges and have particular mechanisms to undergo crosslinking. In the present invention an alternate chemical pathway has been conveniently exploited to incorporate ester linkages into phenolic units. With respect to crosslinked polyesters, this structure is usually achieved by reacting maleic and/or fumaric sites along the polyester backbone with vinylic monomers, of which styrene is most commonly used. In the present invention the versatility of the maleic units has allowed the creation of new polymeric linkages with phenolic molecules.
The literature cites some phenolic polyesters, in some cases chemically modified and crosslinked, and in all cases very different from the polymerization principle involved in the present invention. Hodge and Weimar invented tetramethyladipic acid polyester fibers, and hydroquinone bisphenol A, which remain linear polymers (Ger. Offen.; DE 1937934 700226). Another invention (Das and Prevorsek, U.S. Pat. No. 4,757,118) refers to imide-modified crosslinkable phenolic polyesters. This is a very important innovation in the field of phenolic polyesters, yet the formation of an imide is totally unrelated to the present invention. Furthermore, Japanese workers have invented phenolic polyesters with poly (butylene terephthalate) and a phenolic resin, and obtained a thermoplastic material (Yonetani, Okita, Okita, and Inoe, Jap. Pat 61,168,652 A2 860,730 Showa). Furthermore, a single inventor (Thomas) has made two related inventions. A low-cost polyester modified phenolic resin (U.S. Pat. No. 4,500,689) takes advantage of linseed oil to produce a crosslinked network. The other invention is a phenol-modified a polyester coating containing linoleic acid to promote crosslinking (U.S Pat. No. 4,347,355).
In sum, none of the existing inventions contains solely crosslinked phenolic polyesters, but are either linear polymers (i.e. uncrosslinked) as fibers or thermoplastics, or are crosslinked by conventional modifications (imide formation, or the incorporation of drying oils).